Gastritis due to Helicobacter Pylori is the most common chronic infection in the world today. It has been classified by IARC (WHO) as a Class I human carcinogen. Obviously only a very small portion of the infected population develops gastric cancer. This neoplasia, however, is the second most frequent in the world. In the United States, certain groups display higher risk, especially African Americans, Hispanics, Asian Americans and immigrants from Russia and Eastern Europe. This application addresses the question of different outcomes of H. Pylori infection, which in some subjects leads to gastric carcinogenesis and in others does not. The central hypothesis is that the dichotomy in outcome of the infection is driven by immunologic forces. The proposed small grant application will make it possible to conduct a feasibility study which will determine if a more definitive test of the hypothesis is possible. We will be focused on the cellular-mediated immune response studied in lymphocytes from the peripheral blood and from the gastric mucosa. Two major comparisons will be done: A) In Colombia H. pylori infected subjects living in Nari$o, at very high gastric cancer risk, will be compared with infected subjects living in the coastal city of Cartagena, at very low risk. b) In New Orleans, subjects diagnosed with multiphocal atrophic gastritis (MAG), a cancer precursor lesion, will be compared with subjects with non-atrophic gastritis (diffuse antral gastritis or DAG), which is not associated with increased gastric cancer risk. A full battery of immunologic tests will be carried out to explore if the cytokines characteristic of the T-lymphocyte helper cells responses (Th1 vs. Th2) are different in the contrasting populations. If approved, this application will make it possible to collect the material needed and complement other resources of the department of Pathology to conduct the tests in our laboratories.